1. Field of the Invention
This invention relates to a discharge lamp lighting apparatus, and more particularly, to a discharge lamp lighting apparatus which lights a discharge lamp at a high frequency, can light different types of discharge lamps and can adequately and automatically drive the discharge lamp according to the rating of the discharge lamp.
2. Description of the Related Art
In general, discharge lamps such as fluorescent lamps include preheat start type lamps and rapid start type lamps which are classified according to the starting type thereof. Such discharge lamps have various ratings and include FL (preheat type lamp) 20 type (20W), FLR (rapid start type lamp) 40 type (40W) and FLR 110 type (110W) and the like for respective outputs. The discharge lamps of the above ratings have different voltage-current characteristic curves and therefore they are driven by different inverter devices which have corresponding load curves. For example, the inverter device for the 110W discharge lamp is required to generate a starting voltage of approx. 480V when a load current is 0, and supply a load current of approx. 0.6 A after the discharge lamp is started. Thus, the inverters are required to supply different starting voltages and load currents for respective discharge lamps having different ratings. Therefore, in the prior art, inverter devices are exclusively used for corresponding discharge lamps having different ratings.
However, if different inverter devices are used for respective discharge lamps, the number of types of the discharge lamps increases and it becomes troublesome to use the discharge lamps. Further, it becomes necessary to manufacture various types of inverter devices by a small number for respective types, raising the manufacturing cost of the apparatus and making the apparatus design complicated.